ADT7473ARQZ-1RL ON Semiconductor, ADT7473ARQZ-1RL Datasheet - Page 18

• Manufacturer Part Number: ADT7473ARQZ-1RL
• Description: IC REMOTE THERMAL CTLR 16QSOP
• Manufacturer: ON Semiconductor
• Series: dBCool®r

Specifications of ADT7473ARQZ-1RL

• Function: Fan Control, Temp Monitor
• Topology: ADC, Comparator, Fan Speed Counter, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -40°C ~ 125°C, External Sensor
• Output Type: SMBus™
• Output Alarm: No
• Output Fan: Yes
• Voltage - Supply: 3 V ~ 3.6 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Full Temp Accuracy: +/- 0.5 C
• Digital Output - Bus Interface: Serial (3-Wire, 4-Wire)
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

temperature is clamped to −63°C. In this mode, the diode
fault condition remains −128°C = 1000 0000, while in the
extended temperature range (−64°C to +191°C), the fault
condition is represented by −64°C = 0000 0000.
Temperature Measurement Registers
Register 0x25, Remote 1 Temperature
Register 0x26, Local Temperature
Register 0x27, Remote 2 Temperature
Register 0x77, Extended Resolution 2 = 0x00 default
Bits [7:6] TDM2, Remote 2 Temperature LSBs
Bits [5:4] LTMP, Local Temperature LSBs
Bits [3:2] TDM1, Remote 1 Temperature LSBs
Temperature Measurement Limit Registers
are high and low limit registers. Exceeding the programmed
high or low limit causes the appropriate status bit to be set.
Exceeding either limit can also generate SMBALERT
interrupts.
Register 0x4E, Remote 1 Temperature Low Limit = 0x01 default
Register 0x4F, Remote 1 Temperature High Limit = 0x7F default
Register 0x50, Local Temperature Low Limit = 0x01 default
Register 0x51, Local Temperature High Limit = 0x7F default
Register 0x52, Remote 2 Temperature Low Limit = 0x01 default
Register 0x53, Remote 2 Temperature High Limit = 0x7F default
Reading Temperature from the ADT7473/ADT7473−1
from the ADT7473/ADT7473−1 as an 8−bit value (with 1°C
resolution) or as a 10−bit value (with 0.25°C resolution). If
only 1°C resolution is required, the temperature readings
can be read back at any time and in no particular order.
for each measurement is used. The extended resolution
register (Register 0x77) should be read first. This causes all
temperature reading registers to be frozen until all
temperature reading registers have been read from. This
prevents an MSB reading from being updated while its two
LSBs are being read, and vice versa.
Additional ADC Functions for Temperature
Measurement
ADT7473/ADT7473−1 to offer the system designer
increased flexibility.
Turn−Off Averaging
register, 16 readings have actually been made internally and
the results averaged before being placed into the value
register. Sometimes it is necessary to take a very fast
measurement. Setting Bit 4 of Configuration Register 2
(0x73) turns averaging off.
Associated with each temperature measurement channel
It is important to note that the temperature can be read
If the 10−bit measurement is required, a 2−register read
A number of other functions are available on the
For each temperature measurement read from a value
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18
Single−Channel ADC Conversions
ADT7473/ADT7473−1
conversion mode. In this mode, the ADT7473/ADT7473−1
can be made to read a single temperature channel only. The
appropriate ADC channel is selected by writing to Bits [7:5]
of the TACH1 minimum high byte register (0x55).
Configuration Register 2 (0x73)
Bit 4 = 1, averaging off.
Bit 6 = 1, single−channel convert mode.
TACH1 Minimum High Byte Register (0x55)
Bits [7:5] select the ADC channel for single−channel
convert mode.
Overtemperature Events
channels can be detected and dealt with automatically in
automatic fan speed control mode. Register 0x6A to
Register 0x6C are the THERM limits. When a temperature
exceeds its THERM limit, all PWM outputs run at 100%
duty cycle or the maximum PWM duty cycle (Register 0x38,
Register 0x39, and Register 0x3A) if Bit 3 of Configuration
Register 4 (0x7D) is set. The fans remain running at this
speed until the temperature drops below THERM minus
hysteresis; this can be disabled by setting the boost bit in
Configuration Register 3 (0x78), Bit 2. The hysteresis value
for that THERM limit is the value programmed into the
hysteresis registers (Register 0x6D and Register 0x6E). The
default hysteresis value is 4°C.
Table 8. Conversion Time with Averaging Disabled
Table 9. Conversion Time with Averaging Enabled
Table 10. Programming Single−Channel ADC Mode
for Temperatures
Setting Bit 6 of Configuration Register 2 (0x73) places the
Overtemperature events on any of the temperature
Remote 1 Temperature
Remote 2 Temperature
Channel Selected
Remote Temperature
Local Temperature
Local Temperature
Voltage Channel
Voltage Channel
Channel
Channel
101
110
111
Bits [7:4], Register 0x55
Remote 1 Temperature
Local Temperature
Remote 2 Temperature
into
Measurement Time (ms)
Measurement Time (ms)
single−channel
0.7
1.3
11
39
12
7
7
ADC